The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element ...The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.展开更多
Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic...Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.展开更多
During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredict...During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.展开更多
In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some p...In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some parameter values allowed us to find these high energy pulses. We also found the region in the parameter space in which these solutions exist. Some pulse characteristics, namely, temporal and spectral profiles and chirp, are presented. The study of the pulse energy shows its independence of the dispersion parameter but its dependence on the nonlinear gain. An extreme amplitude pulse has also been found.展开更多
Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a majo...Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.展开更多
A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negat...A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negatively impact processing repeatability and composition control.In this work,singleelement-filled skutterudite is engineered to have high thermoelectric and mechanical performances.Increased Yb filling fraction is found to increase phonon scattering,whereas cryogenic grinding contributes additional microstructural scattering.A peak zT of 1.55 and an average zT of about 1.09,which is comparable to the reported results of multiple-filled SKDs,are realized by the combination of simple composition and microstructure engineering.Furthermore,the mechanical properties of Yb single-filled CoSb_(3) skutterudite are improved by manipulation of the microstructure through cryogenic grinding.These findings highlight the realistic prospect of producing high-performance thermoelectric materials with reduced compositional complexity.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 12102043, 12072375U2241240)the Natural Science Foundation of Hunan Province of China (Nos. 2023JJ40698 and 2021JJ40710)。
文摘The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.
基金This project is supported by National Natural Science Foundation of China(No.50175031).
文摘Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.
基金supported by the National Natural Science Foundation of China(Nos.51921003,51975292 and 52275153)the Outstanding Youth Foundation of Jiangsu Province of China(No.BK20211519)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures,China(Nanjing University of Aeronautics and Astronautics,No.MCMS-I-0521K01)the Fund of Prospective Layout of Scientific Research for Nanjing University of Aeronautics and Astronautics,Chinathe Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.
基金FCT(Fundacao para a Ciência e Tecnologia)for supporting this work through the Project UID/CTM/50025/2013
文摘In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some parameter values allowed us to find these high energy pulses. We also found the region in the parameter space in which these solutions exist. Some pulse characteristics, namely, temporal and spectral profiles and chirp, are presented. The study of the pulse energy shows its independence of the dispersion parameter but its dependence on the nonlinear gain. An extreme amplitude pulse has also been found.
基金supported by the National Natural Science Foundation of China (Nos.52032002 and 51972081)National Safety Academic Foundation (No.U2130103)Science and Technology on Particle Transport and Separation Laboratory,and Heilongjiang Touyan Team Program.
文摘Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.
基金funded by Natural Science Foundation of China(Nos.51774096,51871053)Shanghai Committee of Science and Technology(Nos.16JC1401800,18JC1411200)+1 种基金supported by the NASA Science Missions Directorate under the Radioisotope Power Systems Programsupport from the National Science Foundation(DMREF-1333335 and DMREF-1729487).
文摘A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negatively impact processing repeatability and composition control.In this work,singleelement-filled skutterudite is engineered to have high thermoelectric and mechanical performances.Increased Yb filling fraction is found to increase phonon scattering,whereas cryogenic grinding contributes additional microstructural scattering.A peak zT of 1.55 and an average zT of about 1.09,which is comparable to the reported results of multiple-filled SKDs,are realized by the combination of simple composition and microstructure engineering.Furthermore,the mechanical properties of Yb single-filled CoSb_(3) skutterudite are improved by manipulation of the microstructure through cryogenic grinding.These findings highlight the realistic prospect of producing high-performance thermoelectric materials with reduced compositional complexity.